Method of tawing hides or skins.



UNITED- STATES" PATENT OFFICE.

cnA-nLEs s. DOLLEY AND ALBERT F. CRANK, OFPIIILADETJPHIA, PENNSYLVANIA.

METHOD OF TAWING HIDES OR SKINS.

srncmcs rron forming part of Letters Patent No. 629,124, dated :Tuly 18, 1899.

To all whom it may concern.-

Be it known that we, CHARLES S. D'OLLEY and ALBERT F. CRANK, citizens of the United States, residinga-t Philadelphia. in the county or Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Methods or Processes of Treatiug Hides, Skins, and Leather; and we do declare the following 'to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make andnse the same.

This invention relates to certain new and useful improvements in processes for treating hides, skins, and leather; and the objects of the invention are to provide a process by means of which a superior leather can be produced either from raw hidesor skins or from such hides or skins as have been previously tawed or from such as have been partly but 1 imperfectly tanned and which do not meet the various tests which are commonly employed to determine perfectlytanned leather and which are therefore susceptible to improvement.

Certain varieties of skins (as is the case with E. I. kips andgoatskihs, basils, and white leather) are for convenience of shipment or for other reasons placed upon the market in 3 a taw'ed or an imperfectly-tanned condition. Such skins in many cases do not respond favorably to the usual tests fol-perfect leather, and

hence require subsequent treatment.

Certain methods of tanning throw upon the market a considerable amount of imperfect leather which is susceptible of i mprovementas, fer instance, that treated with cutch or, terra-japonica, divi-divi, &c.-which if properly tanned would command higher prices.

It is one of the objects of the present in: vention to take such tawed and poorly-tanned leather and by proper treatment to convert the same into nearly perfect leather, thus greatly enhancing its value.

The invention has for a further object to fix in the skins or hides such substances-for example, extractives, coloring-matter, fillers,

natural and artificial tannins, &c.'as may.

be employed with the purpose of feeding the leather and of providing it with certain desired physical characterssuch as plumpness,

- Application filed meet 28. 1899. sin-n1 No. 710,818. (No specimens.)

weight, color, softness, impermeability to moisture, &c.

Our invention consists, essentially, of two steps, the first of which is conccrnedwith the introduction into the hide or skin of some material or materials which will render the skin sensitive to the fixing or tanning agent employed in the second step by overcoming the agglutinating action ofthe interfibrillar ground substance (mucin, coriin, &c.) and effect a splitting up of the connective-tissue fiber bundles with an accompanying swelling and separation of the fibers and fibrils, producing thereby. a fulling'or plumping elfect, clearing the grain, and at the same time feeding the leather that is to say, impregnating the skin with materials the presence of which is desirable for the production of the physicalqualities noted above. This first step has the same purpose as that commonly attained by thepemployment of old and sour liquors and weak solutions of extractives nd which precedes the actual tanningproce s. 1

The second step of the process consists'in treating the hide or skin to the action of formic aldehyde, (GH OJ a material possessing the property of fixing the connective-tissue fibers and fibrils inthe swelled and plumped, tawed, or partially-tanned condition produced by the first treatment and at the same time of fixing in, upon, or between the fibers and fibrils of the connective tissues materials which have been supplied by the first step of the process to contribute special physical qualities-much as body, color, su pplencss, weight, &c.essen tial to a solid well-nourished leather. The use of the formic aldehyde in this second step isnota mere aggregation of elements or materials, as it is in its nature and effects entirely different from the materials employed .in the first step and. could not be substituted forthem to produce the effects of the first step, While it possesses distinctive and'posi- -tive characters by which it acts upon both the skin and the materials with which it has been impregnated by the first step in a manner peculiar to itself, as will be hereinafter more fully set forth, and we use formic aldehyde in the second step of onr process strictly as a tanning agent to render the skin non -putrescible and insoluble. w

IOO

In carrying out our invention we take advantage of the property possessedby varions wing. e esi n s elm,

salt, argolf'eggsi fl ouf,"vegetable"einracfivei :ambier, and cutch, and the artificial and nat: ural tannins used in making leather, many of which have none or only feeble tanning prop erties -of icaiis'irigiai swieni'n open separatio 1'1 of the fibers and fibrils of the SkiIl-OQBDQQQWQ tissue and the deposition in, upon, and between the same of aterials prevent them from again' ecomin g aggliiti natedfi thereby all move readi the same 'tii is of advan color, &c.,

owing the interlacing fibers to ly upon each other and which at neZadd-niziterial te tlie skin; which e in ieepeet-zt i e itt; 29%; W

hereby a plump, soft,'pliabl,' wee-e9 estw ather, m y be p e i ctiomega es eem-rem "flatness a O r r we? flour upon the weight of the skins or hides-to be treated also upon their acidity ar alkalinty,

afd c'pidi ng'itoifigell l lj6 gambier tanning .70 rocesses, The skins ides are then age tated in the gambier-bath until they are permeated through and through by the solution forming the bath, the time required dependii-hgisomewhatlupohithe nature of .the particu lar sigins or hides, the size of the receptacle, the number or volume of skins, and the rapidit yvth vghich the receptacle is revolved or c"on' te:nts agi atedgfaetors which do not concern the prin :iple involved in the process. When the gaml ier has struck through or rth'orciughlympermeated tlie skins, which may ascertained, by cutting into the thickest e ataexamm'tg he exposed interior, the

' clean water; but this wash- 'rred,'be dispensed proceeded with atr orbe held to washfe ture -essential to our arl'y 1 de stood that the obtest our process is, as has g ets ed, ogliring the skins hysiha'l' c n'dition, character eparait' and swelling of the dfibrils ndsnch plumpness, ssas'wilhwhenfixed f formic aldehyde, I j'erof the particular we are ableto delsaisig v "11- r s' 't'o s ecure desirablestates l v .v e s p d orsupplem ntedtthereing b y' the'aetion of forniic aldehyde subsequently ap lied in theseconu st iereina te'r'described? I The followin ustrate the' st oinniercial sheep or goat'skins orhides, -havcin t g kvib sl i rreatmen't i .1 e'c essaafy iumsoriireel i wW-hi'c'lt ithyvni'ayibe agitated i :tgbyitheirevolving ofi itherecjeptacle byl-pa'ddles :Orzby any rother suitabl'e'm eans, the particular 1 -metho'd=.or inechanism employedlconstituting ilnqip'a rt of?v ltheibpresent inven tion. We, ihold l Lourselves fre'ei ato employ anyeform of mcepl i'taEi-lendnmethodzdfeagitation hvhagtsoev'eriti Ho-i gethernwith Ethe l'hides-fo kins (fin: itlie rece'rpeta'cleds plapedia ssoitition/oft andhi-er extract i zsu-ificientlyidilu tediftozpresen-tzthe e'xtractlto cheaen tine mas'sgo ,1 t eiislciin s; containing; ap-i cproximately fourspoiiiidsaof 'gambier' tmehch III Eoni'hundredcpoiinds ofrtvet: hides oreskin'sg sthe act eamoumtg at; lga mb;

being men H) n if Lil 1 wi l mime;

.cltinicze-n 1 1 color; weight; 5

egl'" hysicalcharacters by argo1 eggs, flour, the nd' other vegetable exstep; therefore, it is not so istioir ofi the materials employed, 'e'choi'ce i'n this respect, but

e physical qualities in "kin y'vhi'cl'lfeive 'r o'c'eed to supplement, and r'e'tider perni'a'n'e'nt by the second step. The use of saline liquors serves to swell the ssue's and i ibers ofi the skin and to render 'orereadily affectedby'the tanning or fixag'ent tly-"employed, while the ice their equivalents add vegetable ex t'ra'ct f 'llliesecon'dstep .ofour'pirocess consists in subj'ecti n'g theskinsbr hides to the action of formic aldehyde,{preferably in solution, al oughi it' may be employed in the state of gas,

h either-Lin the'sameyreceptaele in which they --were:given' he' pre'l-ifminary treatment or, if desired; i a'specialreceptacle. The amount 'ofv-t'he solution employed varies som ewhat,

butcis'ha'se' 'on theiweight of the skins or hidesito' b' reaited,-tia=nd=zwe have found in 12 5 Epfracti'ceAh-at ithrewp iun'dsl of commercial ent i( t0%)1:formic-aldehyde solution to'zeaclirbne liu ndred pounds of wet hides or skins is sufiicientifor ordinary sheep or goat rski ns flhe amounh df "water with which the ifdr-nn-i aldehfyd'eizis diluted is based upon the 111., just" sufficient to keep ia'nd. .to present th e formic tee time masszor the skins, but

- lar case which is cited herein as an illustration-namely, sheep or goat skinswe have found that the time required is approximately three hours. The time, however, depends to a very considerable extent, as in the treatment by the first step of our process, upon the number of skins in the receptacle and the rate and mode of agitation to which theyrhave been subjected. It is advisable to maintain the bath in the second step at a temperature of not less .than 80 Fahrenheit and not above 120 Fahrenheit in order to secure the gre'atest efficiency from the formic aldehyde, which has greater penetration and less liability to polymerize than at low temperatures. After the skins are found to have beenthorou'ghly fixed by the formic aldehyde they are washed and are then ready for the usual treatment employed in finishing.

In case the formic aldehyde is employed in the state of a gas we prefer the following method: The skins having been brought to the desired state by the first step, as'hereinbefore described, an amount of commercial formic-aldehyde (forty-percent) solution, representing approximately three pounds to each one hundred pounds of wethidesor skins to be treated, is placed in a suitable generator, a variety of which are upon the market,:and the gas generated is allowed'to pass by suitable connections into the chamber containing the skins. preferably maintained at from 110 to 120 Fahrenheit, and the'atmosphere, of the chain ber should also be kept moist, bothjo'fwhich conditions are readilysecured by the admis sion'from time to time of a small quantity of warm aqueous vapor by means of a suitable steam connection. The chamber employed should be a closed one and no larger than-nee essary to allow, the skins .to be fully exposed to the action of the gas. 'If desired, the gas may be admitted to the drumv in which the preliminary treatment took'place or into a,

similar drum and the skins agitated therein, or the skins may be stretched on suitable frames and inclosed within a stationary chamber, in either case beingexposed to the action of the gas until they respond to the usual tests for good 'leathersay for a period of six hours, the time depending, however, on the thickness and character treatment. v

The market supplies certain tawed or imperfectly-tanned skins and hides which have been already subjected to the action of salt and alum, flour, eggs, vegetable extractives, gambier, cutch, tannins, or other materials and which do not constitute high -grade leather, but whichfare susceptible of improvement. The eii'ccts produced on these The temperature ofthis chamber is of the skins under skins are analogous to those produced by the first step of our process, and we find it both possible and ad vautageous to take such skins and after softening them in water proceed to treat them as described in the example cited for treating raw skins, whereby we are able to secure the results of the first step with less time and material than would be required in treating green orraw hides or skins, and in certain cases where the tawed or imperfectlytanned skins or hides have the plumpness, color, weight, &c., desired and which we would have seen red by means of on r first step we inay proceed at once to the second step of the process, which consists, essentially, in the fixation of the natural or added constituents of the skin, substantially as described.

We have found by a large number of practical tests that the actual tanning effect of the natural-tannins as introduced into the skin by the first step of our process may be greatly hastened and augmented by the employment of formic aldehyde in conjunction therewith, as, accomplished by the second step of our process. Thus with the pyrogallol tan nins, a considerable proportion of which possesses little or no tanningpower, a compound is formed-whereby all the tannin is rendered available, and consequently a greater not directly available for tan'ning, can be fixed in :the leather, and again with other (pyrogallol) tannins, the deposit of whites or bloom isiprevented, theellagic acid or catechin being insome way altered and indissolubly bound in combination with: the

skin. substance, as are also certain extract formic aldehyde upon the impregnated collogen of the-skin, whereby an occlusion of the introduced material is brought about; also, by its direct action upon the catechus themselves, whereby they are rendered insoluble and precipitated as a filling and coloring material uponand between the fibers and fibrils of the skin connective tissue, thus effecting what is technically known as feeding the leather. A special. advantage afforded by our process is that it overcomes the obstacles hitherto encountered in the use of materials like divi-divi, which addto the leather substances extremely susceptible to fermentation and which leads to loss of leather in damp weather. Thesuperior bactericidal and antifermentative properties of formic aldehyde prevent this fermentation and the consequent softening of the leather. It also prevents moldingduring the drying of the unfinished leather.

.ives' e. "9., gambierby the action of the Formic aldehyde has the property of fixing the collogen and other gelatinous constituents of the skin in the condition in which they are when subjected to its action, and we have found that it is highly advantageous in using formic aldehyde in the manufacture of leather to prepare the skins or hides by some preliminary treatment, as by our first s tep,

whereby the fibers and fibrils of the connectpounds either, first, from a lack of suitable quality in the agents used in the preliminary treatment, such agents being, for example, salt, eggs, flour, alum, argol, vegetable extrac'tives, gambier, cutch, and such other tannin-containing materials as possess little or no tannin properties, or, second, from lack of sufiicient combination with an agent, such as oak or hemlock tannin, which is potentially capable of'saturating the collogeu and forming therewith an insoluble and imputrescible compound, but which in the skins we pro- .piose to treat has de-facto not fully saturated the colloge-n. Inother words, we propose to ga'pply formic aldehyde to hides or skins containing'a soluble collogen compound or un- We therefore employ processes as produce the qualities peculiar to ordinary salt-and-alum tawed skin's, chamois leather, oil tawed leather, wash-leather,

Knapps leather, &c., or the peculiar-leather resultingfrom the employment of gambier and similar vegetable extracts, or where the fixation of the tissue constituents has been imperfectly accomplished by the ordinary tanning processes. The skins may be specially prepared or tawed skins. Chamois leather, 850., may be taken ready prepared and submitted to the fixing action of formic aldehyde.

Much of the leather commonly regarded as welltanned is open to great-improvement,

andour invention proposes the employment of the ordinary processes of. tanning as our first step, or the taking of commercial leather already prepared by-others and submitting it to the fixing and supplemental action of formic aldehyde as asecond or final step in the production of perfectly-tanned leather.

Our invention therefore involves the use of formic aldehyde subsequent to the use of tawing or tanning materials, and inasmuch as these materials give varying degrees of plumpness, weight, density, and color to hides and skins our invention necessarily involves the use of formic aldehyde in conjunction with all materials producing these effects in accordance with our process, as hereinbefore described.

We do not confine ourselves to the use of any one tawing or tanning, plumping, feeding, or coloring material in conjunction with formic aldehyde, as our process is not limited to the production of any one kind of leather, but is applicable to the production of either light or heavy leather, white or colored, as desiredin fact, to all varieties of leather-and its employment, as herein described, results in a very material saving in time, labor, and

materials.

Having thus described our invention, what we claim to be new, and desire to secure by Letters Patent, is.

1'. The process in' theproduction of leather, which consists in subjecting skins or hides to tawiirg and tanning materials for the purpose of plumping, feeding, weighting or coloring them, and then submitting them to the fixing and tanning action of formic aldehyde.

2. The process in the production of leather,

which consists in subjecting skins or hides to the action of tannin-containing extractives,

whereby they are plumped, fed, weighted or colored, and then subjecting them to the fixing and tanning action of formic aldehyde.

3. The process in the production of leather, which consists in treating hides or skins with a tannin -cont-aining extractive, capable of forming a combination with formic aldehyde, (e. g., gambier,) for the purpose of plumping, feeding, weighting or coloring the and then subjecting the impregnated skin to the tanning' and fixing action of formic aldehyde,

whereby the material with which the skins have been fed, weighted and colored is fixed and occluded in the skin tissue, as the collogen of the skin is rendered insoluble'and non-putrescible. a l j 4. The process in the production of leather,

which consists first in plumping, feeding,. weighting, coloringor raising and clearing the grain of skins or hides by treating them in a bath of such agents, and to such steps as are commonly employed for this purpose, and subsequently fixing the skins or hides in the state thus secured and tanning the same by treating them in a bath of formic-aldehyde.

In testimony whereofwe afiix our signatures in presence of two witnesses.

--CHARLES S. DOLLEY.

ALBERT F. CRANK.

\Vitnesses: OHAs. O. MORTON, II. F. REARDON.

Correct ions in Letters Patent 'No. 629,124.

' It is hereby certified that in Letters Paeent' No. 629,124, granted J my 18, 1899,

upon the application of Chat-less. Dolley and Albert Crank, of BhilaQelphia, Pennsylvania, for an improvement/in Methods of Tawing Hides of Skins, errors appear in the printed Specification requ irin'g correction, as follows: Page 4, lipes 2 and 13, I words a elatinous 7 should read gelat'igenous; and that the said Letters Patent shoula be redd with these corrections thereilithat -the -same may conform tmthe recbrd Signed,'countrsigneiand sealefi this 29th day of Au'g-hst, A. D., 1899. I

WEBSTER DAVIS,

' Assistant Secretary of the Interior.

dbuhterigned A. P. GREELEY,

Aiding Cmnmissio er of Patients.- 

